The present invention relates to a semiconductor integrated circuit, an optical disk recording/playback apparatus using the same, and an optical disk recording method and, more particularly, to a semiconductor integrated circuit by which data recording to an optical disk can be restarted after once interrupted, an optical disk recording/playback apparatus using the same, and an optical disk recording method.
Only a guide groove for guiding a laser beam is formed on the substrate of, e.g., a recordable CD disk or DVD disk before recording. When this guide groove is irradiated with a laser beam subjected to data modulation so as to have high power, the reflection of a recording film changes. Accordingly, recording data such as audio data or video data can be recorded on an optical disk such as a CD or DVD. Also, the recorded data can be played back by using an optical disk playback apparatus.
To record data on an optical disk, an optical disk recording/playback apparatus of a personal computer or the like is used. FIG. 4 shows a personal computer 102 which includes a host CPU 106, buffer circuit 103, keyboard 104, hard disk 105, and the like, and an optical disk 101.
In the personal computer 102, data to be recorded on the optical disk 101 is once stored in the buffer circuit 103. The data stored in this buffer circuit 103 is sequentially recorded on the optical disk 101 at a predetermined rate.
When the data stored in the buffer circuit 103 is recorded on the optical disk 101, the next data is stored in the buffer circuit 103, and the stored data is recorded on the optical disk 101. This operation is repeated to record all data on the optical disk 101.
The host CPU 106, however, must control not only the storage of the data into the buffer circuit 103 but also the keyboard 104, harddisk 105, and the like, and must also perform various other control operations. Therefore, if these control operations and the operation of controlling data storage to the buffer circuit 103 are necessary, the load on the host CPU 106 increases.
Consequently, the rate at which data is transferred to the buffer circuit 103 lowers to make the storage of data in the buffer circuit 103 insufficient, and this interrupts recording to the optical disk 101. This phenomenon is called buffer under run. If this buffer under run occurs and recording is interrupted on, e.g., a CD-R (CD-Recordable) on which data can be recorded only once, this recording is terminated before completion. Since no data can be recorded after that, this CD-R must be discarded.
To avoid this event, the following recording method is used. That is, after recording to an optical disk is once interrupted, the end of recording data (to be referred to as “recorded data” hereinafter) already written on the optical disk immediately before the interruption is detected. Write of recording data (to be referred to as “additional data” hereinafter) to be recorded following the recorded data is started in an unrecorded area connecting to the end of the recorded data.
FIG. 5 shows the main components of a conventional optical disk recording/playback apparatus.
A laser pickup 107 plays back recorded data already written on an optical disk 101 before interruption and outputs an analog playback signal. The obtained playback signal is amplified by an RF amplifier 108, and A/D-converted, i.e., binarized by a binarizing circuit 109 included in a sampling circuit 102, thereby obtaining a digital playback signal.
A PLL circuit 110 performs sampling for this digital playback signal, and outputs the sampled playback data. This sampled playback data is supplied to a synchronous detection circuit 111 to generate a playback sync signal of the recorded data.
The sampled playback data is also supplied to a data demodulation circuit 112 to generate a sampling clock of the recorded data. The thus generated playback sync signal and sampling clock of the recorded data are supplied as recording timing data to a recording controller 113.
In accordance with this recording timing data, the recording controller 113 performs timing control for recording additional data. More specifically, the recording controller 113 gives a data modulator 114 a phase control signal containing information pertaining to a recording timing. By using recording data supplied from a buffer circuit 103, the data modulator 114 generates and outputs additional data at a timing corresponding to the phase control signal. The interrupted recording is restarted by recording this additional data on the optical disk 101 via a recording strategy 115, a laser driver 116, and the laser pickup 107.
As shown in FIG. 6, a delay time DELAY1 is produced by the playback signal processing from the timing at which the recorded data is picked up from the optical disk to the recording restart timing and to the playback data generation timing. This delay time DELAY1 includes a time delay1 required for the processing in the RF amplifier 103 and binarizing circuit 109, and a time delay2 required for the processing in the PLL circuit 110.
Also, as shown in FIG. 7, a delay time DELAY2 is produced by the recording signal processing from the timing at which the additional data is modulated to the timing at which the modulated data is written on the optical disk. This delay time DELAY2 includes a time delay3 required for the processing in the recording strategy 115, and a time delay4 required for the processing in the laser driver 116.
As shown in FIG. 8, offsets must be given to the playback signal detection timing, additional data generation timing, and recording restart timing by taking account of the delay times DELAY1+DELAY2 as described above. Hence, the optical disk recording/playback apparatus is designed by taking these offsets into consideration.
These offsets are controlled by measuring the delay times DELAY1+DELAY2 and matching the additional data generation timing with the recording restarting timing, in the stage of designing the optical disk recording/playback apparatus. The general method of matching is to once interrupt recording on an optical disk, and play back the connected portion in which additional data is recorded, thereby checking matching of the timings from, e.g., the waveform of the playback signal or the error rate of the playback data. Unfortunately, this method cannot accurately evaluate matching of the timings.
Also, the delay time delay1 shown in FIG. 6 and the delay time delay4 shown in FIG. 7 vary in accordance with the analog characteristics of individual devices and signal paths. That is, the delay time changes in accordance with, e.g., variations in the characteristics of individual devices and fluctuations in the operating temperature. Therefore, the additional data generation timing and the recording restart timing cannot be accurately controlled only by initial settings in the designing stage.